Serial dilution calculator
Set the fold and the number of steps; get the volume to carry across, the diluent per tube, and where the series ends.
Free, no account needed. Nothing you type is sent anywhere or stored — the arithmetic runs in your browser.
Inputs
Results
Transfer each step
0.1mL
- Diluent per tube
- 0.9mL
- Concentration at the last tube
- 0.001
The arithmetic
Every tube starts with the same volume of diluent, and you carry volume ÷ fold across from the one before. A ten-fold series in 1 mL tubes means moving 100 µL each time into 900 µL. After n steps the concentration is the starting one divided by the fold raised to n — which is why a long series gets away from you quickly.
Where a series actually goes wrong
Almost never the arithmetic. Change the tip at every step. The film left on the outside of a tip carries concentrated material into the next tube, and at high fold that carryover is larger than the volume you meant to transfer — the bottom of the series ends up far stronger than the numbers say, and it looks like a flat dose-response curve rather than a pipetting error.
Mix each tube properly before drawing from it, too. An unmixed tube gives every tube after it the wrong starting point, and the mistake compounds down the row.
The last tube
If you transfer out of the final tube it ends up short by the transfer volume. Either stop transferring at the last one, or make it up — whichever you do, make it the same way every time so a series is comparable with the one you ran last month.